Starter motors for internal combustion engines

ABSTRACT

A starter motor for an internal combustion engine includes a rotatable shaft and a pinion assembly rotatable with the shaft. The pinion assembly is movable axially relative to the shaft from a rest position to an operative position wherein in use the pinion of the pinion assembly engages the toothed wheel of the engine which is to be started. The portion of the shaft along which the pinion assembly moves includes a region of reduced diameter which commences adjacent the pinion of the pinion assembly, when the pinion assembly is in its rest position, and which terminates within the pinion assembly when the pinion assembly is in its operative position. The region of reduced diameter may be constituted by several smaller regions spaced apart by lands the diameter of which is equal to the diameter of the remainder of the shaft.

United States Patent Bowcott [4 1 May 16, 1972 '[54] STARTER MOTORS FOR INTERNAL COMBUSTION ENGINES [72] Inventor:

[73] Assignee: Joseph Lucas (Industries) Limited, Birmingham, England [22] Filed: Nov. 10, 1970 [21] Appl.No.: 88,365

Roy Price Bowcott, Solihull, England [30] Foreign Application Priority Data Nov. 20, I969 Great Britain ..56,822/69 [52] U.S. Cl ..290/38, 290/37, 290/48, 310/83 [51] Int. Cl ..F02n 11/14 [58] Field of Search ..290/37 R, 38 R, 28, 48; 74/421 A; 310/75, 83

[56] References Cited UNITED STATES PATENTS 3,084,561 4/1963 Mattson ..290/38 R X 3,223,863 l2/l965 Preece et al ..290/38 R X Primary Examiner-Lewis H. Myers Assistant ExaminerH. Huberfeld Attorney-Holman & Stern [5 7] ABSTRACT A starter motor for an internal combustion engine includes a rotatable shaft and a pinion assembly rotatable with the shaft. The pinion assembly is movable axially relative to the shaft from a rest position to an operative position wherein in use the pinion of the pinion assembly engages the toothed wheel of the engine which is to be started. The portion of the shaft along which the pinion assembly moves includes a region of reduced diameter which commences adjacent the pinion of the pinion assembly, when the pinion assembly is in its rest position, and which terminates within the pinion assembly when the pinion assembly is in its operative position. The region of reduced diameter may be constituted by several smaller regions spaced apart by lands the diameter of which is equal to the diameter of the remainder of the shaft.

7 Claims, 5 Drawing Figures Patented May 16, 1972 3,663,825

INVENTOR 1 ATTORNEYS STARTER MOTORS FOR INTERNAL COMBUSTION ENGINES This invention relates to starter motors, for internal combustion engines, of the kind, including a rotatable shaft and a pinion assembly rotatable with the shaft, the pinion assembly being movable axially relative to the shaft from a rest position to an operative position, wherein in use the pinion of the pinion assembly engages the tooth wheel of the engine to be started.

A problem exists in starter motors of the kind specified in that in adverse weather conditions the pinion assembly may be prevented from moving from its rest position to its operative position by ice forming on the shaft, and it is an object of the present invention to minimize this problem.

According to the invention in a starter motor of the kind specified, that part of the shaft along which the pinion assembly moves from its rest position to its operative position includes a region of reduced diameter, said region of reduced diameter commencing adjacent the pinion of the pinion assembly with the assembly in its rest position, and terminating within said pinion assembly when said pinion assembly is in its operative position.

One example of the invention is illustrated in the accompanying drawings, wherein,

FIG. 1 is a side elevational view of a starter motor,

FIG. 2 is a fragmentary diagrammatic, part sectional representation of part of the starter motor shown in FIG. 1,

FIG. 3 is a view similar to FIG. 2 of an alternative arrangement, and

FIGS. 4 and 5 are views similar to FIGS. 2 and 3 respectively of a modification.

Referring first to FIGS. 1 to 3 of the drawings, the starter motor includes a casing 11 having a shaft 12 journalled for rotation therein. The shaft 12 is supported in bearings in the casing, one of the bearings being shown at 13. Mounted for axial movement on the shaft 12 adjacent the bearing 13 is the pinion assembly including a pinion l4, and adjacent the pinion 14 the casing 11 is cut away to expose the pinion. The pinion assembly further includes a roller clutch which permits the pinion 14 to rotate relative to the shaft 12 in one direction, the roller clutch transmitting rotation of the shaft 12 to the pinion 14 in the other direction, so that the pinion 14 rotates with the shaft 12 in said other direction. In use, the starter motor is mounted adjacent the toothed fly wheel of an internal combustion engine, and the pinion assembly 14 is movable from a rest position, as shown in solid lines in the drawings, wherein the pinion is spaced from the toothed wheel of the engine, to an operative position, as shown in broken lines in the drawings, wherein the pinion 14 is engaged with the toothed wheel of the engine, rotation of the shaft 12 when the pinion is in its operative position serving to crank the engine.

The pinion assembly is movable from its rest position to its operative position by means of a solenoid mounted on the casing 11. The solenoid includes a plunger which is moved axially when the solenoid is energized, and which is coupled to the pinion assembly to a lever arrangement. Thus, when the solenoid is energized the pinion assembly is moved axially with respect to the shaft, from its rest position towards its operative position. The plunger of the solenoid further serves to control a switching device which in turn controls energization of the starter motor. The switching device may be of a single stage type wherein the starter motor is not energized until the pinion is fully engaged with the toothed wheel of the engine, whereupon the starter motor is energized at its full torque value. Alternatively the switching device may be of a two stage type wherein the starter motor is energized at a low torque value when the pinion has been moved through a predetermined distance, and is then energized at its full torque value when the pinion fully engages the toothed wheel of the engine. In addition the pinion assembly and the shaft are provided with mating, quick pitch screw threads which, when the pinion engages the toothed flywheel, with the shaft rotating, drives the pinion assembly axially into full engagement with the flywheel.

In conventional starter motors the portion of the shaft 12 along which the pinion 14 is moved from its rest position to its operative position is plain, and in adverse weather conditions ice can form on this portion of the shaft. The formation of a layer of ice on this portion of the shaft can prevent movement of the pinion from its rest position to its operative position, and thereby prevent operation of the starter motor to start the associated internal combustion engine.

In the construction shown in FIG. 2 of the drawings, the portion of the shaft between the rest position of the pinion and operative position of the pinion includes a region 15 of reduced diameter. The region 15 is so positioned on the shaft 12 that one end of the region 15 is within the pinion 14 when the pinion is in its rest position, while the other end of the region 15 is within the pinion 14 when the pinion 14 is in its operative position. It should be noted, however, that the pinion 14 is part of a pinion assembly, which engages the shaft 12 at the side of the region 15 remote from the bearings 13, even when the pinion 14 is in its operative position. Thus, although the region 15 of the shaft 12 does not support the pinion 14 throughout its movement from its rest position to its operative position, the pinion is supported in its operative position by a portion of the shaft 12 adjacent the bearings 13, and by the portion of the shaft 12 on the side of the region 15 remote from the bearing 13.

When ice forms on the shaft 12, it will form in a layer of substantially uniform thickness, and the difference in diameter between the shaft 12 and the region 15 of the shaft 12 is chosen to be equal to, or slightly greater than, the maximum thickness of the ice layer which is likely to form on the shaft 12. Thus, since the pinion 14 extends over the region 15 when the pinion assembly is in its rest position, then the layer of ice which is formed on the region 15 of the shaft 12 will not impede the movement of the pinion 14. When the solenoid is energized to operate the starter motor, the pinion assembly will be moved relative to the shaft 12 towards its operative position, and the pinion will not be impeded by ice until the outermost end of the pinion 14 reaches the end of the region 15 adjacent the bearing 13. By this time, the pinion assembly, the lever arrangement, and the plunger of the solenoid will have achieved sufficient momentum to break up the ice layer on the portion of the shaft 12 between the end of the region 15, and the operative position of the pinion 14. Moreover, in a system employing a two stage switching device, the action of the quick pitch thread on the shaft and the pinion assembly will aid the full engagement of the pinion with the engine flywheel.

In the alternative arrangement shown in FIG. 3, the region 15 is divided into two separate portions 15a, 15b by a generally centrally positioned land 16 of diameter equal to the diameter of the remainder of the shaft 12. The portion 15a terminates, at its end adjacent the bearing 13, within the pinion 14 when the pinion 14 is in its operative position, and the portion 15b commences, at its end remote from the bearing 13, within the pinion 14 when the pinion 14 is in its rest position. Thus during movement of the pinion assembly 14 from the rest position to the operative position, the pinion 14 will not be impeded until the pinion engages the land 16. The momentum achieved by the plunger of the solenoid, the lever arrangement, and the pinion assembly during the movement of the pinion from its rest position to the point at which it engages the land 16, is sufficient to break the ice from the land 16 so that the pinion passes over the land 16. After passing over the land 16 the pinion will not be impeded again until it engages the portion of the shaft 12 adjacent the bearing 13, at which time the momentum achieved by the assembly will again be sufficient to break the ice from this region of the shaft 12. If desired the region 15 of the shaft 12 can be divided into more than two separate portions provided that the lands defined between the regions are not large enough to permit the formations of ice layers sufficiently large to arrest the progress of the pinion assembly.

Moreover, it is not essential that the region 15 or separate regions 15a, 15b etc. commence within the pinion in the rest position of the pinion assembly, provided that the land prior to the commencement of the reduced region or regions is of such a length that the force generated by the solenoid to move the pinion assembly is sufficient to break an ice layer formed on the land.

In the modification illustrated in FIGS. 4 and 5 the groove and the grooves 15a, 15b, are filled to the level of the remainder of the shaft 12 with a synthetic resin material to which ice does not adhere strongly and which will not weld to the material from which the pinion assembly is constructed. Suitable synthetic resin materials include polytetrafluoroethylene and nylon. This modification can of course be applied to an arrangement having more than two separate portions in the region 15 of the shaft 12.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. A starter motor including a rotatable shaft and a pinion assembly rotatable with the shaft, the pinion assembly being movable axially relative to the shaft from a rest position to an operative position, wherein in use the pinion of the pinion as sembly engages the toothed wheel of an engine to be started, that part of the shaft along which the pinion assembly moves from its rest position from its operative position including a region of reduced diameter, said region of reduced diameter commencing adjacent the pinion of the pinion assembly with the assembly in its rest position, and terminating within said pinion assembly when said pinion assembly is in its operative position.

2. A starter motor as claimed in claim 1 wherein said region of reduced diameter commences within the pinion assembly when the pinion assembly is in its rest position.

3. A starter motor as claimed in claim 1 wherein said region of reduced diameter comprises a pair of portions of reduced diameter separated by a land of diameter equal to the diameter of the remainder of the shaft.

4. A starter motor as claimed in claim 1 wherein said region of reduced diameter includes a plurality of portions of reduced diameter separated by lands and diameter equal to that of the remainder of the shaft.

5. A starter motor as claimed in claim 1 wherein the region of the shaft of reduced diameter is filled to the level of the remainder of the shaft with a synthetic resin material to which ice cannot adhere strongly and which will not weld to the material of the pinion assembly.

6. A starter motor as claimed in claim 5 wherein said synthetic resin material is polytetrafluoroethylene.

7. A starter motor as claimed in claim 5 wherein said synthetic resin material is nylon.

* l =i t i 

1. A starter motor including a rotatable shaft and a pinion assembly rotatable with the shaft, the pinion assembly being movable axially relative to the shaft from a rest position to an operative position, wherein in use the pinion of the pinion assembly engages the toothed wheel of an engine to be started, that part of the shaft along which the pinion assembly moves from its rest position from its operative position including a region of reduced diameter, said region of reduced diameter commencing adjacent the pinion of the pinion assembly with the assembly in its rest position, and terminating within said pinion assembly when said pinion assembly is in its operative position.
 2. A starter motor as claimed in claim 1 wherein said region of reduced diameter commences within the pinion assembly when the pinion assembly is in its rest position.
 3. A starter motor as claimed in claim 1 wherein said region of reduced diameter comprises a pair of portions of reduced diameter separated by a land of diameter equal to the diameter of the remainder of the shaft.
 4. A starter motor as claimed in claim 1 wherein said region of reduced diameter includes a pluralitY of portions of reduced diameter separated by lands and diameter equal to that of the remainder of the shaft.
 5. A starter motor as claimed in claim 1 wherein the region of the shaft of reduced diameter is filled to the level of the remainder of the shaft with a synthetic resin material to which ice cannot adhere strongly and which will not weld to the material of the pinion assembly.
 6. A starter motor as claimed in claim 5 wherein said synthetic resin material is polytetrafluoroethylene.
 7. A starter motor as claimed in claim 5 wherein said synthetic resin material is nylon. 